Many attempts have been made to develop a satisfactory operating system for temporarily bringing the doffer and associated feed mechanism to slow or creep speed to permit adjustments or repairs to be made such as the putting up of an end of sliver. While it is not necessary with standard cards, which operate at slower speed, to reduce the doffer and associated feed mechanism to slow or creep as for such purposes, with high speed carding it is necessary to reduce the output of the card to provide sufficient time to re-establish the web and to place the sliver in the coiler head. An attempt has been made to use an alternating current motor drive for the doffer which is independent of the main cylinder as well as other driving components of the card. Due to the characteristics of an alternating current motor, however, the acceleration from slow speed to operating speed occurs too quickly causing a jerking action resulting in unevenness and thin places in the web. An attempt to utilize a direct current motor operated independently of the main cylinder for driving the doffer at all times has met with limited success. Due to the characteristics of the direct current motor, it is difficult to maintain the required degree of uniformity of speed in order to be compatible with the other driven components of the card. Therefore, it is necessary to monitor electronically the speed of the direct current motor at all times. Furthermore, direct current motors tend to have a short useful life when put to such use making frequent and expensive replacement necessary.
Accordingly, it is an important object of this invention to provide a card drive facilitating the operation of the doffer and associated feed mechanism at slow or creep speed for permitting necessary alterations to the card and for returning the doffer and associated feed mechanism to operating speed without producing excessive undesirable web variations.
Another important object of the invention is the facilitating of carding operations wherein the doffer is run at reduced speed in order to permit repairs to be made in such a way that the doffer may be returned with controlled uniform acceleration to operating speed after which the other card driving mechanisms may be utilized for driving the doffer at operating speeds.
Still another important object of the invention is the provision of a control mechanism permitting the utilization of a direct current motor for independently operating the doffer and associated mechanism at low speed, returning the doffer to run speed and then discontinuing the operation of the direct current motor permitting utilization of the regular card drive for operation of the doffer at operating speeds.